This invention is generally directed to toner and developer compositions, and more specifically the present invention is directed to novel thermotropic liquid crystalline polymers, and processes for the preparation thereof. The thermotropic liquid crystalline polymers of the present invention are preferably random copolymers, and more preferably random copolyesters with three or more spacer groups therein many of which are as illustrated in FIGS. 1 to 16. The aforementioned polymers can be selected as resins for toner compositions, including magnetic, single component, and colored toner compositions. In one embodiment of the present invention, the low melting toner compositions are comprised of the thermotropic liquid crystalline random copolyesters resin particles illustrated herein, pigment particles, and optional additive particles. There are also provided in accordance with the present invention positively charged toner compositions comprised of the thermotropic liquid crystalline resin particles illustrated herein, pigment particles, and charge enhancing additives. In addition, the present invention is directed to developer compositions comprised of the aforementioned toners, and carrier particles. Furthermore, in another embodiment of the present invention there are provided single component toner compositions comprised of the thermotropic liquid crystalline resin particles illustrated herein, magnetic components such as magnetites, and optional additive particles. The toner and developer compositions of the present invention are useful in electrophotographic imaging and printing processes, especially xerographic processes. Further, the developer compositions of the present invention possess stable electrical properties for extended time periods, and in some instances with these compositions, for example, there is no substantial change in the triboelectrical charging values.
Although liquid crystalline polymers are generally known and can be selected as films or resin toners, in many instances these polymers possess inferior mechanical, transport and/or storage properties, that is agglomeration results with extended storage, and moreover such polymers in some instances possess high melting properties, that is a melt temperature above 100.degree. C. and thus are melt processable at from about 130.degree. to 300.degree. C. In contrast, the polymers of the present invention are melt processable, for example, at from about 90.degree. to about 130.degree. C. Specifically, toner compositions with certain liquid crystalline thermotropic polymers are illustrated in U.S. Pat. No. 4,543,313, the disclosure of which is totally incorporated herein by reference. The aforementioned polymers do not contain three spacer groups therein and further do not possess many of the advantages associated with the thermotropic liquid random copolyesters of the present invention which exhibit low melting properties. Also, the polymers of the '313 patent do not contain two different spacer groups. Accordingly, with the polyesters of the present invention and the toner compositions thereof, agglomeration and physical or mechanical integrity, particularly at temperatures of from about 40.degree. to about 75.degree. and preferably about 60.degree. C., are retained and these materials exhibit low thermal properties such as low melting temperatures, low softening point temperatures and low viscosities at temperatures at from between about 55.degree. to 105.degree. C. and more preferably between about 60.degree. and about 95.degree. C. enabling them to be more readily melt processable. Specifically, the thermotropic liquid crystalline copolyester polymers of the present invention possess acceptable glass transition temperatures of up to about 75.degree. C. and preferably from about 40.degree. to about 60.degree. C., and low melting temperatures of from about 55.degree. to about 105.degree. C. and preferably from about 60.degree. to about 95.degree. C.
Other references of interest which disclose the use of amides as toner additives include U.S. Pat. Nos. 4,072,521; 4,073,649; and 4,076,641. Furthermore, references of background interest are U.S. Pat. Nos. 3,165,420; 3,236,776; 4,145,300; 4,271,249; 4,556,624; 4,557,991; and 4,604,338.
Also, there was selected as a result of a patentability search U.S. Pat. Nos. 4,514,540; 4,617,371; 4,687,360; and 4,729,847. The '371 patent discloses polymeric liquid crystals which contain mesogene and spacer units in alternating sequence, which polymers may further contain aliphatic substituents. The spacer moieties may be compounds with a flexible hydrocarbon chain with terminal functional groups at both ends of the chain that react under appropriate reaction conditions to form linkages with the mesogenic monomers, see column 5, lines 38 to 43, for example. The '540 patent relates to a copolymer reaction product useful in flexographic ink compositions, which copolymer contains up to 25 percent of a synthetic polymeric resin with a crystalline chain structure. Resin components employed in the preparation of the polymeric compositions of this patent include, for example, copolymers of styrene or acrylate/methacrylate esters with acrylics. There is disclosed in the '847 patent a chiral liquid crystal substance with an optically active group and a chiral liquid crystal composition containing the aforesaid group. Also, there is disclosed in this patent the selection of various esters for the synthesis of the optically active compound. In the '360 patent, there is disclosed a thermal transfer ribbon including a partially crystalline polymer, which polymer can be derived from an acid containing at least one carboxylic acid moiety.
Moreover, toner and developer compositions containing charge enhancing additives, especially additives which impart a positive charge to the toner resin, are well known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of certain quaternary ammonium salts as charge control agents for electrostatic toner compositions. There is also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica. Further, there is illustrated in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer and toner compositions having incorporated therein as charge enhancing additives organic sulfate and sulfonate compositions; and in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions containing resin particles and pigment particles, and as a charge enhancing additive alkyl pyridinium compounds, inclusive of cetyl pyridinium chloride.
Other prior art disclosing positively charged toner compositions with charge enhancing additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; and 4,394,430.
Although the above described toner and developer compositions are useful for their intended purposes, there is a need for improved compositions. More specifically, there is a need for toner compositions, including single component compositions which possess some advantages not achievable with the prior art compositions including lower melting temperatures of from about 55.degree. C. to about 105.degree. C. There is also a need for thermotropic liquid crystalline polymers with three or more spacer groups. In addition, there is a need for toner and developer compositions that maintain their triboelectrical characteristics for extended time periods exceeding, for example, 100,000 developed images. Furthermore, there is a need for single component toners, and colored toners that possess many of the aforementioned characteristics. Also, there is a need for positively charged toner compositions with charge enhancing additives therein.